what-is-plate-tectonics.pdf

Plate Tectonics → a theory which suggests that Earth’s crust is made up of plates that interact in various ways, thus producing earthquakes, mountains, volcanoes and other geologic features. Crust → made of a variety of solid rocks; average density of 2.8 g/cm3 and its thickness ranges from 5 to 5...

Plate Tectonics → a theory which suggests that Earth’s crust is made up of plates that interact in various ways, thus producing earthquakes, mountains, volcanoes and other geologic features. Crust → made of a variety of solid rocks; average density of 2.8 g/cm3 and its thickness ranges from 5 to 50 km. → It is thickest in a part where a relatively young mountain is present and thinnest along the ocean floor. a. Continental Crust → the thick part of the Earth’s crust, not located under the ocean; less dense. b. Oceanic Crust → the thin part of the Earth’s crust located under the oceans; denser  According to the plate tectonics model, the entire lithosphere of the Earth is broken into numerous segments called plates.  There are 7 relatively large plates and a number of smaller ones, including the Philippine plate. The plates move very slowly but constantly and this movement is called tectonic; thus the theory of moving lithospheric plates is called plate tectonics.  3 types of seismic waves; P, S and L waves. The first two travel into the Earth’s interior while the last one on the surface. These waves travel at different velocities; thus, do not arrive at a seismic recording station at the same time. The difference in the arrival time will tell us the distance of the earthquake’s focus from the seismic recording station but it does not tell in which direction it came from.  If we have at least three recording stations that can tell how far away from them the earthquake occurred, the epicenter can be determined using the triangulation method. 1. It uses the distance information from three seismic stations to locate the earthquake epicenter. 2. On a map, circles are drawn around each seismic station. 3. The radii of the circles are scaled to the estimated distance from the station to the earthquake. 4. The three circles will intersect at one point that locates the earthquake.